This invention relates to snow skis and more particularly to lightweight, honeycomb laminated skis.
Skis are generally constructed by laminating various layers to a core material to form a material composite which may exhibit a wide range of structural characteristics. Wood, metal and plastic materials have been used to form ski cores onto which fiber reinforced resins may be laminated. Metal honeycomb has been found particularly suitable as a core material because of its good flexibility, high shear strength and low weight. U.S. Pat. No. 3,740,301 discloses a honeycomb core material having fiberglass resin laminates wrapped about the honeycomb core in a box configuration. Such a box configuration generally adds to the stiffness of the ski in all directions.
Further contributing to both the sidewall and the vertical stiffness of the skis are metallic edges extending along the length of the ski to form a running surface edge. Such edges are necessary not only to provide protection to the ski from wear, but also to provide a biting edge to prevent sliding on turns. One-piece metallic ski edges, however, greatly affect the vertical and sidewall flexibility of a ski. For example, a typical modulus of elasticity of a ski composite without a steel edge may have an E modulus in order of 14 .times. 10.sup.3 psi while the same ski with a one-piece steel edge may exhibit a modulus of 36 .times. 10.sup.3 psi. A further disadvantage of the one-piece steel edge is that where flexible skis are designed; a large amount of strain may occur under relatively low stresses, such strain being beyond the yield point of the steel edge, resulting in permanent deformation of the ski. To overcome the above disadvantages of the one-piece steel edge, and yet provide a continuous metal edge for protection and good tracking on turns, the so-called "cracked-edge" has been developed. By cracking the running surface edge, the stresses are interrupted and a greater elongation of the sections is obtained without the high stress present in a continuous steel strip which could cause permanent deformation. Such edges have been manufactured with an L cross section wherein the outer, thicker portion makes up the running surface edge while the thinner portion is inserted into the ski body and interconnects the segments of the running portion. Various segment spacings and interconnection configurations have been suggested to provide various flexural and damping characteristics. For example, in U.S. Pat. No. 3,401,949, a cracked edge is disclosed having a relatively thick arcuate interconnecting section. Such an edge provides good vertical flexibility but maintains the segmented edges in substantial alignment, thus greatly decreasing a ski's sidewall deflection which uses such an edge. U.S. Pat. No. 3,700,252 teaches variable size segments to provide different flexing and damping characteristics in various portions of the ski.
Ski designers have in the past concentrated on obtaining certain longitudinal and torsion flex characteristics and have allowed these properties to dictate the amount of sidewall deflection. Exactly how these properties affect the overall performance of a ski must be viewed in terms of the overall ski design.
The overall shape of a ski is designed to distribute the force exerted by the skier throughout the length of the ski. Thus, a ski is generally cambered with its thickest vertical portion in the middle where the skier's weight is localized. Also, the horizontal width of a ski in the middle portion is often tapered inward forming a "waist" to provide the ski with good turning characteristics. For advanced skiers, ski flexibility, especially in the sidewall direction, was never considered an important property. However, for the beginning and intermediate skier, and even for the more advanced "bump skiers" who want a relatively long ski for downhill speed yet require a ski which can go over numerous bumps and negotiate quick turns, sidewall deflection has been found to be very desirable. Previously, ski designers concentrated on longitudinal and torsional flex characteristics giving little attention to the sidewall deflection of the ski. For ski designers using wooden or plastic cores, the sidewall deflection was generally predetermined. With the use of stiff wooden cores, it is generally impossible to design a ski with any appreciable amount of sidewall deflection. Utilizing foam or plastic cores, both the top and sidewalls must be designed to increase the strength of the ski, since the core itself does not provide sufficient shear strength in any direction to permit its use without reinforcement.
It is an object of this invention to provide a lightweight, high strength ski which exhibits excellent flex characteristics in both the longitudinal and sidewall direction without loss of desired torsional properties.